Target 1: Kaburi Anorthosite Project by GlobalMin Ventures
Within the PGGS area, an anorthositic body of rock in the Kaburi River basin has emerged as a highly-prospective PGM target. The Kaburi anorthosite is a 2.1-2.2 billion-year-old portion of a layered mafic intrusion, and it is the anorthositic portion of intrusions like this that host PGM “reefs” in the Bushveld of South Africa and the Stillwater in Montana. Within the same Guiana Shield greenstone terrain that hosts the Kaburi anorthosite, a platiniferous layered mafic intrusion is also present across the border in Venezuela. Goldfields indicated anecdotally to Dr. Lechler, that approximately 1M ounces of Pt were thought to be present in the soils overlying that intrusion, called Mochila.
Throughout northern Guyana alluvial sediments in places contain abundant platinum, palladium, and minor rhodium, but not ruthenium, osmium, nor iridium, indicating that the bedrock source of these alluvial minerals is a layered mafic intrusion, not an alpine or zoned ultramafic intrusion. Mineralogy of the alluvial PGMs determined by GlobalMin includes an abundance of minerals found in Bushveld’s Merensky Reef, including Rustenburgite, Atokite, and others, again presenting the signature of a layered mafic intrusion like the Bushveld. Kaburi River sediments immediately downstream of the anorthosite have been found to contain anomalous PGEs, with Pd dominating over Pt, suggesting groundwater leakage of PGEs from buried mineralization in the anorthosite, since Pd is generally more soluble than Pt. PGM abundances are typically dominated by Pt in rocks and soils within the PGGS area.
Much of the Kaburi anorthosite is overlain by a thick blanket of exotic quartz sand that is approximately 50 ft. thick in much of the area. Since no soil is accessible for sampling in these areas, GlobalMin used a biogeochemical technique of sampling leaves of the Yari-Yari tree along 2-3 mile long survey lines from the Kaburi River to the east over the anorthosite to sense bedrock chemistry through the exotic overburden. Absent the quartz sand overburden, GlobalMin sampled soils to infer the underlying bedrock composition, a well-tested, reliable exploration method. Each of these geochemical survey lines contains 1-3 platinum anomalies along with the other elements expected to be present if PGM reef-type mineralization exists. Moreover, ground magnetic surveying indicates that the tree leaf and soil chemistry is reflecting characteristics of the underlying bedrock, confirming the efficacy of these geochemical surveying techniques. The geochem lines show clear, distinct anomalies of platinum within a uniform background line, accompanied by relatively clear Ni-Co-Cu-Ir-Te-and/or Bi anomalies and somewhat noisier Pd and Rh distributions. PGM mineralization is typically enriched in these related elements.
Interpretation and Conclusions of the Sampling Program
Target 1 at Kaburi is the classic and most sought-after type of PGM mineral deposit, the anorthosite-hosted PGM reef, in the style of the Merensky in the Bushveld and the J-M in the Stillwater layered mafic intrusion of Montana. That being true, the Kaburi anorthosite in the Kaburi River basin in Guyana has become an exciting PGM target due to the early exploration results indicating the possible presence of a PGM reef. The Kaburi anorthosite appears to be a tilted portion of a layered mafic intrusion of the same 2.1-2.2 Ga age as the platiniferous Mochila layered intrusion in the Venezuelan portion of the Guiana Shield.
The presence of the White Sand Series overlying the anorthosite in much of the area required the use of biogeochemical surveying to sense the chemistry of bedrock through the exotic overburden in the first two geochemical lines, but soil geochemistry was used in the third, southernmost line. Platinum anomalies are present in all three lines, and line up to define what appears to be a linear zone of PGM mineralization accompanied by the commonly-related elements Ni-Co-Cu, extending for at least four miles. This hypothesized reef would be a planar feature parallel to the originally-horizontal igneous layering, both of which now appear to be tilted at a relatively high angle. Fan-drilling into the mineralization in several places along strike should quickly characterize the thickness, geometry, and grade of any bedrock PGM mineralization.
Our Exploration Plan
Target 1 consists of the Kaburi anorthosite in which biogeochemical and soil geochemical surveying indicates a linear Pt anomaly over a distance of at least four miles. The anorthosite is 2.1-2.2 billion years old and is a tilted portion of a layered mafic intrusion. Linear Pt mineralization in the Bushveld and Stillwater intrusions are the economic Merensky and J-M reefs, respectively, hosted in the anorthositic portions of these layered mafic intrusions. Therefore, the working hypothesis at the Kaburi anorthosite is that a PGM reef is present. This planar feature is expected to be dipping at a fairly high angle to the west, coming nearly to the surface where it is covered by saprolitic soil and/or unconsolidated white sand approximately 50 feet thick.
The company has three E-W geochem lines defining this reef-like feature but plans to collect additional geochem survey lines prior to commencing drilling. This is not a lengthy process and can be completed by the time drill rigs are on site and ready to start drilling.
At least two lines of drill holes trending N-S are planned to intersect and characterize the geometry and composition of the hypothesized reef. The topographic relief in the area is moderate, with rolling hills separated by swampy lowlands. Drill positioning will be dictated by surface geochem results and practical aspects of positioning rigs on solid ground. Initial drilling results will dictate subsequent activities.
Kaburi Anorthosite Exploration Data
The following images show the thoroughness with which our exploration program determined that Kaburi is a prime target for further exploration.